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Search Results: 1 - 10 of 26 matches for " Kaspars Blush "
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Sub-Doppler spectroscopy of Rb atoms in a sub-micron vapor cell in the presence of a magnetic field
David Sarkisyan,Aram Papoyan,Tigran Varzhapetyan,Janis Alnis,Kaspars Blush,Marcis Auzinsh
Physics , 2003, DOI: 10.1088/1464-4258/6/3/023
Abstract: We report the first use of an extremely thin vapor cell (thickness ~ 400 nm) to study the magnetic-field dependence of laser-induced-fluorescence excitation spectra of alkali atoms. This thin cell allows for sub-Doppler resolution without the complexity of atomic beam or laser cooling techniques. This technique is used to study the laser-induced-fluorescence excitation spectra of Rb in a 50 G magnetic field. At this field strength the electronic angular momentum J and nuclear angular momentum I are only partially decoupled. As a result of the mixing of wavefunctions of different hyperfine states, we observe a nonlinear Zeeman effect for each sublevel, a substantial modification of the transition probabilities between different magnetic sublevels, and the appearance of transitions that are strictly forbidden in the absence of the magnetic field. For the case of right- and left- handed circularly polarized laser excitation, the fluorescence spectra differs qualitatively. Well pronounced magnetic field induced circular dichroism is observed. These observations are explained with a standard approach that describes the partial decoupling of I and J states.
Magnetic field-induced mixing of hyperfine states of Cs 6 2^P_{3/2} level observed with a sub-micron vapor cell
Aram Papoyan,David Sarkisyan,Kaspars Blush,Marcis Auzinsh,Daniel Bloch,Martial Ducloy
Physics , 2003,
Abstract: The fluorescence spectra of a sub-micron atomic cesium vapor layer observable under resonant excitation on D2 line have been studied in the presence of an external magnetic field. Substantial changes in amplitudes and frequency positions of the individual (resolved) hyperfine transitions have been recorded in moderate magnetic fields (up to ~ 50 Gauss). These features are caused by mixing of the hyperfine states of the upper level resulting from comparable values of the hyperfine splitting of the 62^P_{3/2} manifold and Larmor frequencies of the magnetic sublevels. The results of simulation show a good agreement with the experimental spectra. Possible application of the results for high spatial resolution magnetometry is discussed.
Anthropogenic Influence on the Dynamics of the River Lamprey Lampetra fluviatilis Landings in the River Daugava Basin
Janis Birzaks, Kaspars Abersons
Scientific Journal of Riga Technical University. Environmental and Climate Technologies , 2011, DOI: 10.2478/v10145-011-0025-z
Abstract: The construction of the Daugava hydro power station (HPS) cascade has significantly transformed Latvia's largest river the Daugava, reducing its importance in the natural reproduction of anadromous fish species. Currently in Latvia, as well as in other Baltic Sea countries, the river lamprey catch is decreasing, whereas the landings in the river Daugava have tended to increase. The dynamics of the river lamprey landings show the possible redistribution of lamprey stocks between the rivers Gauja and the Daugava. Possibly, this is a result of anthropogenic influence and changes in the river lamprey resource management may be necessary in the future.
Diversity of pili-specific bacteriophages: genome sequence of IncM plasmid-dependent RNA phage M
Rumnieks Janis,Tars Kaspars
BMC Microbiology , 2012, DOI: 10.1186/1471-2180-12-277
Abstract: Background Bacteriophages of the Leviviridae family are small RNA viruses with linear, positive-sense, single-stranded RNA genomes that encode only four proteins. All phages of this family require bacterial pili to attach to and infect cells. Leviviridae phages utilizing F-pili for this purpose have been extensively studied. RNA phages specific for conjugative plasmid-encoded pili other than that of plasmid F have been isolated, but are much less understood and their relation to the F-pili-specific phages in many cases is not known. Results Phage M has the smallest known Leviviridae genome to date and has the typical genome organization with maturation, coat and replicase genes in the 5′ to 3′ direction. The lysis gene is located in a different position than in other known Leviviridae phages and completely overlaps with the replicase gene in a different reading frame. It encodes a 37 residue long polypeptide that contains a transmembrane helix like the other known lysis proteins of leviviruses. Sequence identities of M proteins to those of other phages do not exceed 25% for maturation protein, 51% for coat protein and 41% for replicase. Similarities in protein sequences and RNA secondary structures at the 3′ untranslated region place phage M together with phages specific for IncP, IncC and IncH, but not IncF plasmid-encoded pili. Phylogenetic analysis using the complete genome sequences and replicase proteins suggests that phage M represents a lineage that branched off early in the course of RNA phage specialization on different conjugative plasmids. Conclusions The genome sequence of phage M shows that it is clearly related to other conjugative pili-specific leviviruses but has an atypical location of the lysis gene. It provides a better view on the remarkable diversification of the plasmid-specific RNA phages.
Validity of Rate Equations for Zeeman Coherences for Analysis of Nonlinear Interaction of Atoms with Laser Radiation
Kaspars Blushs,Marcis Auzinsh
Physics , 2003, DOI: 10.1103/PhysRevA.69.063806
Abstract: In this paper we, to our knowledge, for the first time obtain the rate equations for Zeeman coherences in the broad line approximation and steady-state balance equations directly from optical Bloch equations without the use of the perturbation theory. The broad line approximation allows us to use the adiabatic elimination procedure in order to eliminate the optical coherences from the optical Bloch equations, but the steady-state condition allows us to derive the balance equations straightforward. We compare our approach with the perturbation theory approach as given previously and show that our approach is more flexible in analyzing various experiments. Meanwhile we also show the validity and limitations of the application of the rate equations in experiments with coherent atomic excitation, when either broad line approximation or steady-state conditions hold. Thus we have shown the basis for modeling the coherent atomic excitation experiments by using the relatively simple rate equations, provided that certain experimental conditions hold.
Luminescence of alpha-quartz
Anatoly Trukhin,Kaspars Truhins
Physics , 2012,
Abstract: Among the host materials luminescence the luminescence of the self-trapped exciton (STE) is reviewed. This luminescence, which band is situated at 2.6 to 2.7 eV, could be observed mainly under ionising radiation with energetic yield about 0.2. The STE does not participate in pure recombination processes. Host material defect luminescence at 5 eV appears in alpha-quartz after heavy irradiation. It is constituted of permanent defect after neutron irradiation and transient defect after dens electron beam irradiation. This luminescence could be observed well at temperatures below 60 K. All another luminescence are of impurity nature. The Ge impurity luminescence in alpha-quartz explained as STE near Ge. The aluminium and alkali complexes. One of them is with UV band at 6 eV, appears at low temperatures and could be excited only in tunnelling recombination process between pairs (AlO4 Me), where Me is an alkali ion captured an electron and a hole remains on aluminium tetrahedron. Another luminescence with band at 3.4 eV is also luminescence of complexes (AlO4 Me), which behaviour is similar to the luminescence of alkali alumosilicate glass. The third luminescence with band at 3 eV could be observed mainly in natural alpha-quartz, bright at temperatures below 200 K and is interpreted as STE like luminescence at alumosilicate clasters. The exchange of alkali ions to noble ions of copper of silver reduces original luminescence of alumo alkali complexes and luminescence of noble ions appears. The main band of copper related luminescence is at 3.4 eV and that of silver is at 4.75 eV, both could be observed up to 500 K. their nature could be well described in terms of intraions transition. Exchange of noble ions back to alkali ions renews initial luminescence of the samples.
Quantum Lower Bound for Graph Collision Implies Lower Bound for Triangle Detection
Kaspars Balodis,Jānis Iraids
Computer Science , 2015,
Abstract: We show that an improvement to the best known quantum lower bound for GRAPH-COLLISION problem implies an improvement to the best known lower bound for TRIANGLE problem in the quantum query complexity model. In GRAPH-COLLISION we are given free access to a graph $(V,E)$ and access to a function $f:V\rightarrow \{0,1\}$ as a black box. We are asked to determine if there exist $(u,v) \in E$, such that $f(u)=f(v)=1$. In TRIANGLE we have a black box access to an adjacency matrix of a graph and we have to determine if the graph contains a triangle. For both of these problems the known lower bounds are trivial ($\Omega(\sqrt{n})$ and $\Omega(n)$, respectively) and there is no known matching upper bound.
Self-Enhancement of Scalar and Vector Holographic Gratings in Azobenzene Molecular Glassy Films  [PDF]
Andris Ozols, Valdis Kokars, Peteris Augustovs, Dmitrijs Malinovskis, Kaspars Traskovskis, Elmars Zarins, Girts Ivanovs
Optics and Photonics Journal (OPJ) , 2014, DOI: 10.4236/opj.2014.46015
Abstract:

Self-enhancement (SE) effect of scalar and vector holographic gratings (HG) recorded in three different azobenzene molecular glassy films is experimentally studied in both transmission and reflection modes at 532 and 633 nm. The maximal SE factor (the ratio of diffraction efficiency to its initial value) SEF = 42 has been achieved. It is shown that the model of complementary HG can be applied also in scalar transmission thin HG case to explain coherent SE. The possibility of vector HG coherent SE in transmission mode is experimentally demonstrated for the first time (SEF = 4.3). The possibility of coherent HG SE in reflection mode is also established for the first time (SEF = 21). HG recording processes as well as coherent SE processes are found to be independent in transmission and reflection modes being determined by volume and surface relief HG, respectively. The permittivity gradient mechanism is proposed to explain the coherent SE of surface relief HG. Both HG recording and coherent SE efficiencies strongly decrease when HG period is decreased from 2 mm to 0.5 mm. No relaxational SE effect is found. Coherent SE effect in molecular glasses is found to be weaker than in inorganic materials.

Manipulation of Dark States and Control of Coherent Processes with Spectrally Broad Light
Marcis Auzinsh,Nikolai Bezuglov,Kaspars Miculis
Physics , 2008, DOI: 10.1103/PhysRevA.78.053415
Abstract: The formation of dark states under interaction of degenerate atomic states with incoherent broadband radiation (white light) is discussed. A simple coupling scheme in a three level Lambda-system, which allows both qualitative and quantitative analysis is discussed. We found a stationary solution of the optical Bloch equations in a broad excitation line approximation that describes the dynamics of the atom-white light interaction and demonstrated its identity to a conventional dark state created with coherent laser fields. We than examine the efficiency of the population transfer induced by broadband radiation in a model Lambda-system and revealed that high efficiency (attaining 100 percent) of stimulated Raman adiabatic passage-like processes can be achieved with certain temporal control of light polarization. The corresponding criterion of adiabaticity was formulated and justified by means of numerical simulations.
Temporal and Spatial Variation of Nutrient Leaching from Agricultural Land in Latvia: Long Term Trends in Retention and Nutrient Loss in a Drainage and Small Catchment Scale
Viesturs Jansons, Ainis Lagzdins, Laima Berzina, Ritvars Sudars, Kaspars Abramenko
Scientific Journal of Riga Technical University. Environmental and Climate Technologies , 2011, DOI: 10.2478/v10145-011-0028-9
Abstract: Agricultural run-off monitoring and losses of nitrogen (N), phosphorus (P) from small (60 - 960 ha) catchments and drainage fields (12 - 77 ha) in Latvia were analyzed. The catchments represent areas with different agricultural production intensity, landscape, soils and climate. Results from the long-term monitoring show (i) large differences in levels of losses between the catchments and fields with different farming intensity, (ii) large annual and interannual variability due to climate impact and soil conditions, (iii) few time trends in nutrient losses. These results are discussed in relation to pollution from non-point and point sources. Besides, these data demonstrate changes in agriculture driven by large-scale changes in land-use intensity. However, despite the increased implementation of mitigation methods by farmers, improvements in water quality at the catchment scale can take a long time. Long-term monitoring programmes to detect trends are required.
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